The invention relates to a coolant circuit for an internal combustion engine, including a liquid coolant with a coolant radiator having a radiator line and a bypass line, by way of which coolant can by-pass the radiator. The coolant flow through the bypass line is controllable as a function of temperature via a thermostatic valve which has a flow connection to the radiator line, a connection to the bypass line, a further connection to a supply line or removal line on the internal combustion engine, and a connection to a connecting line which leads from a mixing chamber to a heating circuit and is intended for generating a temperature control flow on the expansion element. The heating circuit has a heating valve for controlling the coolant flow in the heating circuit, and the thermostatic valve has a thermostatic operating element which is arranged in the mixing chamber and is provided with a main valve disk controlling the flow connection to the radiator line with a short-circuit valve disk controlling the flow connection to the bypass line.
DE 102 06 359 A1 discloses such a coolant circuit with a thermostatic valve arranged on the motor outlet side. The thermostatic valve has an expansion element which is connected to a main valve disk and a short-circuit valve disk (two-disk thermostatic valve) in such a manner that, after a cold start, the main and short-circuit valves are initially closed by the main and short-circuit valve disks, so that the coolant circuit is interrupted (full throttling of the coolant circuit). With increasing heating of the internal combustion engine, first of all the short-circuit valve for a coolant circuit between internal combustion engine and by-pass line is opened and, with further heating of the internal combustion engine, the main valve is subsequently opened and the short-circuit valve closed again.
So that, when the coolant circuit is interrupted, the coolant which is warming up can nevertheless reach the expansion element in a controlled manner, a temperature control line leading into the heating circuit is attached to the mixing chamber. This temperature control line can be used to generate, in a controlled manner, a small coolant flow in the mixing chamber, causing the expansion element to initiate further control movements.
DE 197 25 222 A1 discloses a thermostatic valve with an expansion element for controlling a main and a short-circuit valve. The short-circuit valve has a short-circuit valve disk which is held on the expansion element in a manner such that it can be displaced relative thereto and which is biased in the closing direction by a spring. During a cold start, both the main valve and the short-circuit valve are closed, so that the coolant circuit is blocked. The spring loading the short-circuit valve disk is configured in such a manner that it keeps the short-circuit valve closed up to a predetermined partial-load rotational speed of rotation of the internal combustion engine and only then, as a result of a rise in pressure in the coolant circuit, is the short-circuit valve disk displaced in the opening direction against the force of the spring.
Disadvantages of a thermostatic valve of this type are its complicated structural design and the only relatively small degree of accuracy obtainable for the opening and closing times for the valve disks.
It is therefore the object of the present invention to provide an improved coolant circuit for internal combustion engines with a plurality of cylinder banks, which is simplified in its design and control and by which the engine warm-up period is shortened.